Fun Facts About Fluorescent Light Bulbs

Particularly since compact fluorescents are the rage (thanks, Jerry!):

Fluorescent lamps are relatively sensitive to ambient temperature because they are low pressure lamps. Optimum lamp operating temperature is 5-25 degrees Celsius. Above this limit the efficacy falls by approx. 1 % for every degree rise. Below this limit the efficacy fails by approx. 5% for every degree fall. Fluorescent lamps should be protected from draughts that can reduce lamp wall temperature and light output.

Overvoltage to the ballast will cause high tube current shortens lamp and ballast life. It also causes preheat lamps to start like instant start lamps - shortens lamp life.

Undervoltage to the ballast causes low tube current - makes lamps flicker, causes uncertain starting and reduces light output. Undervoltage to the ballast can cause preheat starters to recycle - shortens starter and lamp life.

Fluorescent lamps are affected by extremes in ambient temperature. They operate best in the range 5-25 (35 for High Output T5) degrees Celsius. Below this there is a rapid drop in light output and difficulty in starting.

High humidity causes electrical leakage along the lamp surface - lowers the starting voltage provided by the ballast. Lamps are pre-coated with silicone to break up the moisture film and prevent such leakage.

Fluorescent Lamp Advantages:

Fluorescent lamps are 3-7 times more efficient than incandescent lamps.

Power consumption for equal light output is much less than for an incandescent lamp.

Rated lamp life is between 5,000 and 18,000 hours, depending on style, approximately five to eighteen times longer than typical incandescent lamp life.

Lamps can be selected for desired colour rendering purpose e.g. aquaria.

Available with wattage ratings from 4 to 125W. (There are 215W High Output and Powergroove lamps but these will not operate on conventional European control gear.)

Low surface brightness provides better visual comfort and diffused lighting.

Optional dimmable ballasts are available. Lamp colour does not significantly change when dimmed. Power consumed is proportional to light output.

Fluorescent Lamp Disadvantages:

Variations in supply voltage affect lamp light output and starting.

Required external equipment (ballast) consumes energy, adds to equipment cost. For retro-fits, establishes lamp size and wattages that can be used.

Lamp frequency flicker can cause discomfort to some people.

Operation on a range of supply voltages requires different control gear components or more expensive tapped ballasts.

Ballasts may produce irritating 100HZ humming sound - only reliable solution is to replace ballast.

Lamps are large for the amount of light produced - HID and incandescent lamps are much more compact.

Radio frequency interference from lamps may disturb communications equipment at close range. Note there are new EMC (Electro Magnetic Compatibility) Regulations due to come into force for the EU.

Distracting lamp flashing can occur with a glow starter attempting to strike a failed lamp.

Stroboscopic effects can make rotating machinery appear stationary which could be a potentially dangerous situation.